Increasing numbers of vehicles come equipped with some form of “telematics” service platforms. Telematics services are those services enabled by a three-way marriage among vehicles, computing and communication technologies, and is sometimes used to mean the wireless linkage of vehicles to data networks, particularly the internet. These telematics service platforms are able to carry out various intelligent transportation system services, such as reporting a vehicle's status and position to a service center and provide certain applications such as emergency and safety assistance. In the next few years, more telematics products will be made available and eventually, most if not all vehicles will have some form of telematics platform that will offer various services, such as emergency services (e.g., emergency communication in the event of an incident, such as airbag deployment), navigation services, concierge and transaction services (e.g., restaurant information, hotel reservation), communication and personal information services (e.g., E-mail, calendar services), information services (e.g., stock information, personalized news, sightseeing information), entertainment services (e.g., interactive games, music downloads), and so forth.
These telematics service platforms require the use of some type of wireless communication. Since wireless communication is generally expensive relative to non-wireless communication (e.g., cellular phone calls versus land line phone calls), the ability of these telematics products to use wireless communication options in the most cost effective manner will be an important factor in the success of vehicular telematics. By wireless communication options, it is meant the various wireless communication networks available, discussed below, the various levels of service that each type of wireless communication network has available (i.e. transmission power level), as well as any other option that may now be available or will be available in the future for wireless communication.
In the near future, a variety of wireless communication options will be available for use by wireless communication devices in vehicles, such as satellite, cellular phone and short-range radio frequency (RF) links. These systems differ in cost, bandwidth and coverage. For example, in urban areas and along the major highways, emerging technologies, such as GPRS (general packet radio service) will be deployed in the U.S. in the next few years and will offer “always-on connections” and packet oriented data communications at higher bandwidths than today. Improved code division multiple access (CDMA) technology such as W-CDMA will also likely be established. Also, the Ricochet 2 metropolitan area access (MAN) wireless network will soon be available in 48 major metropolitan areas in the United States covering a very large percentage of the population. These new wireless networks typically provide a higher bandwidth than existing wireless networks, such as the first generation cellular network (AMPS—Advanced Mobile Phone System) and the second-generation cellular networks (GSM—Global System for Mobile Communications; CDMA—Code Division Multiple Access; and TDMA—Time Division Multiple Access).
A general method to evaluate the existing and emerging wireless communication networks and services for data communication is to examine their cost and performance levels. The first generation AMPS cellular systems typically have a maximum data transfer rate of 9600 bps and the second generation digital wireless communication systems have a maximum bandwidth of 14.4 kbps. The new third generation cellular systems will have maximum bandwidths of around 128 kbps or even 384 kbps. Since the charge for cellular communication is high, particularly when compared to even interstate land line phone calls, the cost for transferring data using these systems can be quite high. For example, the cost to transfer one mega-byte of data using the second generation digital wireless communication systems runs around $15.00 or higher. If a mobile user wants to obtain a large amount of content, the cost of doing so with cellular wireless communication can be quite high, making mobile data communication involving large amounts of data cost prohibitive to many potential users.
FIG. 1 provides a general illustration of the presently available wireless communication systems. They include regional area wireless networks 10, wide area wireless networks 12, metropolitan area networks 14, and local area networks 16. Regional area wireless networks 10 provide coverage over a large geographic region, such as the coverage provided by satellite based cellular communication networks and its cost varies greatly. Wide area networks 12 are exemplified by the existing land based cellular phone systems mentioned above. They provide coverage over a relatively large geographic region, but to a lesser extent than regional area networks because the wide area networks utilized land based base station systems that individually have only a small geographic coverage. To obtain the wide area coverage, multiple base station systems must be spread throughout the coverage area with some degree of overlap in coverage. Thus, the geographic coverage provided by a given cellular phone system is often determined by population density and/or travel density in that locating base station systems in sparsely populated, lightly traveled geographic areas may not be cost justified. Metropolitan area networks 14, as the name implies, provide coverage only in metropolitan areas. The most well known type of metropolitan area network is Metricom's Richochet2 network architecture. Wireless local area networks 16 provide very limited geographic coverage, typically on the order of 100 yards or less. Because of this limited geographic coverage, wireless local area networks have not been used to any extent in mobile communications and their application has been pretty much limited to use in office environments and the like where the work stations that are connected to the wireless local area network are located in close proximity to each other. One such of wireless local area network is the 802.11 wireless LAN.
Initially, when the cellular systems first became popular, the wide area network AMPS network was used. More recently, cellular systems have added the second-generation digital networks to the wide area networks being used as well as the satellite based regional area networks and the metropolitan area networks. As these additional networks have been added to the networks available for mobile communication use, cellular in particular, mobile communication devices such as newer generation cell phones have been provided the capability to switch between various networks. For example, a cellular phone can utilize the first generation AMPS network or the second generation digital networks (such as GPRS, GSM and CDMA), and even the satellite based networks.
When the mobile communication device switches among wireless networks, this is known as vertical handoff. A simple form of vertical hand-off would involve a cell phone having multi-network capability selecting which network to use based upon factors such as cost, availability and performance and switching to a second network if coverage from the first network is lost. Vertical handoff is more than just the ability to use more than one wireless network. In this regard, the cellular phone must maintain the same phone number even when it has switched networks. For example, a user having a cell phone that has both analog and digital capability might select the digital network if it was available because it has better quality than the analog network, but select the analog network if digital coverage was not available. (In today's environment, the analog network has broader coverage than digital coverage.)
More sophisticated mobile communication devices will perform the vertical handoff automatically. For example, if a cellular phone has tri-mode capability of using the analog network, digital network, and satellite network, the phone might select the network to use based in order of preference and availability. The user would have entered an order of preference into the phone telling it to use the analog network if its available, then the digital network and then the satellite network. Assuming that the phone first connected to the analog network, the phone would switch to the digital network if the user moves out of the analog coverage area, and then to the satellite network if the user moves out of both the analog and digital coverage area. Typically, the phone decides to switch based upon whether it is in the coverage area of a given network usually determined by signal strength from the network's antennas. One of the problems that this technique has is that by the time a determination is made that the network being used should be switched, there may be a loss of service due to the time that it takes to make the switchover. Also, if the switch is from a more expensive network to a lesser expensive network, such as from the satellite network to either the digital or analog network, the switch from the satellite network may not be accomplished when the user first enters the coverage area for the analog or digital network, resulting the user paying longer than necessary for the more expensive satellite network.
Vertical handoff is a well-understood technology in the mobile computing field. In general, it is about how to automate the connection status and routing table updates on top of the mobile Internet Protocol (Mobile IP) technology. However, due to the unpredictable nature of wireless network boundaries, there is often an abrupt cut-off of service when the boundary is reached. Consequently, the overall direction of vertical hand-off research is generally focused on quick recovery schemes, such as preventative multicast to neighboring base stations.
Accordingly, it is an objective of the present invention to provide a predictive method of achieving seamless vertical handoff in a wireless communication system.
It is a further objective of the present invention to utilize the bandwidth available with local area networks for mobile communication, even though the geographic coverage of local area networks is limited.